Many electro-magnetic type fuel injectors are configured such that when a current is applied to a coil winding within the fuel injector, a magnetic field is generated that urges the pintle/ball assembly away from the nozzle seat and thereby turns the injector ON. In general, the amount of force needed to lift a pintle/ball assembly from the injector OFF or closed position to the injector ON or open position is proportional to a pintle return spring force plus a fuel pressure of the fuel present in the injector. However, some direct injection fuel systems have increased fuel pressures to a level where it becomes difficult to provide a fuel injector that has the same physical outline or package size as injectors designed for lower fuel pressure levels, and is able to reliably ‘dead lift’ the pintle/ball assembly at the higher fuel pressure levels.
It has been proposed to add a sliding armature, also known as a decoupled armature or flying armature, that in response to the magnetic field, accelerates towards and strikes a pintle stop like a slide hammer to provide a combination of kinetic energy and static force to lift the pintle/ball assembly off the nozzle seat. However, the additional mass of this armature undesirably increases the impact force of the pintle/ball assembly on the nozzle seat when the fuel injector is turned OFF, which may lead to the ball bouncing back off the nozzle seat, thereby resulting in unmetered fuel being dispensed, or fuel being dispensed that is not properly atomized. This temporary movement of the pintle/ball away from the seat may also be referred to as pintle bounce. Elimination or reduction of this unmetered fuel may also reduce injector to injector flow variation. The increased impact force may also lead to undesirable noise and/or reduced injector life.